Extinguishing hydrocarbon fires is achieved by gas phase interruption of the free radical chain reaction in the oxidation process. The conventional methods of extinguishing hydrocarbon fires involve the use of extinguishing agents, such as, the Halon 1301-type and water-based foams. Halon designates extinguishant of polyhalogenated hydrocarbons containing fluorine, chlorine, and bromine. Another extinguishant of the described type is Halon 1211 which is bromochlorodifluoromethane. Extinguishing burning solid propellants, since solid propellants contains their self contained fuels and oxidizers, places these materials in a different category from the usual hydrocarbon air fires.
Because of the extremely, rapid burning rate of solid propellants, a means to bring an effective extinguishant to the burning sites of propellant fires in a fraction of a second to extinguish the propellant fire is a minimum requirement for effectiveness. Meeting this requirement is recognized as a major advancement which would yield an important contribution to this area of fire control.
Solid propellant burns at a higher rate when it is confined than when it is in an open area or when unconfined; however, when solid propellant is burning in an open area and when the pressure drops below a minimum value to sustain flame burning, such as by smoldering, may still take place. Thus, a special technique would be required to extinguish even the smoldering solid propellant since solid propellant has both the fuel and oxidizer needed to sustain combustion without an outside source of oxidizer or fuel.